The invention relates to a semiautomatic or fully automatic firearm, in particular in the form of a rifle or a pistol, containing a barrel whose rear barrel end is in the form of a cartridge chamber into which a projectile can in each case be inserted from the rear; a breech body which is arranged in a breech guide between the cartridge chamber and a rear wall such that it can move in the longitudinal direction between an open position, which releases the cartridge chamber in order to load a projectile, and a closed position which closes the cartridge chamber, wherein, in the closed position, the breech body closes the cartridge chamber at the rear and is used as an opposing bearing for the cartridge case.
The invention relates to a firearm with a locked breech and to firearms with an unlocked breech.